Since I bought the 300D I have the same question as you... But I think I found an answer now!!!
I started with the low budget version Tamron 70-300 which is rather cheap but image quality is not that great. Also slow and unprecise AF
is a problem with this lens. After that I tried a lot. I bought Sigma APO II
70-300 which is ok and has also a good price but it wasn't good enough for me. I also had some AF
problems with this one.
Then I lend a Canon 28-300 IS USM
! This was the best I've ever had on my cam but if you check out the price: 2300€!!! Thats way too much I think.
So I tried the smaller sister the 75-300 IS USM
! And I bought it some days ago and I'm very very happy with it. It has a precise AF
, picture stabilizer and a great picture quality also beween 200-300mm...
Go for it, if you can afford it, if not get the Canon 75-300 USM
! Half the price without the stabilizer but also good picture quality.
Hope this helps...
@Clickhappy: That looks cool; do you often go to the gym